Computer applications are pieces of computer software that help a user thereof perform a task or a number of related tasks. In the electronic environment of today, these applications are often provided in such a way as to be accessible to a number of users. To accomplish this, a provider of the application may host the application from a particular location that is accessible via a network, such as a local area network or wide area network, such as the Internet.
In hosting the application, the provider usually hopes to attain a state in which the application is available to users in a continuous manner. However, sometimes problems arise that may cause availability to be interrupted. For example, a catastrophic disaster, such as an earthquake, fire, etc., could occur at the primary host site. In the alternative, the machine or machines may experience hardware and/or software malfunctions that cause the application to cease performing. Alternatively, communications between the host site and the network may be lost, resulting in an inability of users to access the application. When these events occur, providers often perform disaster recovery to restore application functionality to users. Often this disaster recovery includes executing the application at a secondary site where it has previously been stored.
One more recent solution (described in U.S. patent application Ser. No. 12/955,483 provides a solution for implementing disaster recovery for an application. A subscription backup site for the application is selected from among a plurality of sites. The site that is selected will have a virtual space that is able to accommodate the workload requirements for the application. The application is deflated on the site in such a way as to operate in a dormant state. In the dormant state, the application has a small fraction of its required resources allocated to it. Thereafter, when disaster recovery is needed, the application can be inflated on the subscription backup site by allocating resources to enable the application to execute on the subscription backup site.
One technical challenge that can occur during disaster recovery involves the manner in which the application is located for access by users when the execution of the application moves from the primary site to the backup site. For example, an internet protocol (IP) address can be assigned to an entire server, e.g., the primary site. In many applications, the IP address of this server must be unique (on a public network) to those accessing the server. For this reason, in these applications, the backup site cannot be actively using the IP address at the same time as the primary site (unless the subnet remains unroutable). However, when disaster recovery is required, a user that attempts to access an application on the backup site should be able to do so using the IP address that is familiar to the user, e.g., that of the primary site.